The Experiment
by immaculately-flawed
Summary: Sherlock needs John for an experiment. John discovers that he likes being tied up. Sexy times ensue. Sherlock/John. Rated M for language and slash.
1. Chapter 1

**A/N:** Ok, so for anyone who has read my other stories. This is NOT like those! I was feeling grumpy and edgy and wrote what pretty much amounts to porn. Plot is kept to a minimum to maximize smutty sex scene. :P This was written for a picture prompt that I can't put here cause a) it's a picture and b) it's hotter than the sun but totally inappropriate for this site.

I'd like to thank my wonderful beta Rheadyn and applaud the fact that our friendship lasted through that awkward moment when your friend confesses that she just wrote a kinky sex fic. :)

**Disclaimer:** Sherlock is not mine, I'm just playing with the characters.

**Warnings:** Slash and bondage… if that's not your cup of tea, I suggest you run away like the hounds of Baskerville are after you.

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><p><strong>The Experiment<strong>

"John, I need you for an experiment."

"What kind of experiment?" John asked warily. He had learned his lesson about Sherlock and experiments… the hard way.

"This one won't turn your hair green, I promise." _Well, that was reassuring at least._

Sherlock didn't wait for his consent, —when did Sherlock ever wait for consent?— just grabbed John by the shoulders and spun him so that he was facing the wall. John's arms were pulled behind his back and he experienced a moment of pure shock as he realized what was going to happen a moment before it did. Something rough and firm, a belt perhaps, was looped around his wrists and pulled tight.

"Uh, Sherlock? What are you doing?"

"Isn't it obvious? I'm recreating the crime scene."

John swallowed as he remembered exactly _what_ the crime scene had been like.

"I'd like to unvolunteer for this experiment." John said thickly.

He was spun around again to face Sherlock whose eyes were brimming with barely suppressed excitement.

"Come now, John, there are lives at stake."

"You're only saying that to make me comply."

"Yes." Sherlock grinned evilly. "Now get on your knees."

John's knees hit the floor. Not because Sherlock had told him to —Okay, maybe a little because of that— but because most of the blood in his legs was quickly relocating to… other areas.

_Being tied up by your insane flatmate is not sexy_, John told himself strictly. _I beg to differ_, said the more honest part of his brain. _I'm not even gay_, he reminded that part. _No, you just find Sherlock's deep voice, big hands and icy eyes extremely arousing._ John felt like banging his head against a mental wall; trust Sherlock to force him into a sexual identity crisis against his will.

"Right, so he was on his knees, we know this from the scratches on the skin. And he was naked, of course." Sherlock looked at John contemplatively.

"Sherlock, no!" John said, a little panicky. "I am not getting naked!"

"You're not being very cooperative, John." Sherlock pouted.

"You're not being very reasonable!"

"Fine, just your shirt then." And without giving him any time to protest Sherlock quickly unbuttoned John's shirt and slipped it down his arms.

John's mouth was very dry and his rather unprofessional interest in the proceedings was beginning to show.

Sherlock didn't seem to notice.

"Next, they interrogated him. But he wouldn't give them the information. No, he was tougher than that, stubborn too. So they beat him. Here" Sherlock swiped one polished Italian shoe across John's stomach, the cool leather making his muscles quiver. "Here." He touched the overly sensitive tissue around John's scar. "And here." His fingers brushed across John's cheek, then his lips. The touch was almost clinical in nature but it sent John's heart into overdrive.

"Of course, that didn't yield any results." Sherlock continued, pacing.

Oh, it was yielding results alright. John was now fully aroused and his groin was throbbing in time with his heartbeat. And all he could think about was that he was on his knees. Tied up. Vulnerable. With Sherlock towering above him, in control and dictating logic in that sexy voice he reserved for murder cases.

"So what would they do next? They couldn't kill him, not right away, they needed the information."

Sherlock stepped in front of him and suddenly John's eyes were level with Sherlock's crotch. And that sent his mind down paths it had no right treading. But then Sherlock slid one long-fingered hand into John's hair and his breath caught in his throat because, no, Sherlock couldn't—

His head was tugged back till he was looking up into Sherlock's frustrated gaze.

"Are you paying attention, John? This is important." He said.

"Uh—" John gave himself a hundred points for not moaning.

"Think, John. Think! What are we missing?"

"More rope." _Also his brain. Did he just say that out loud?_

Sherlock blinked which was code for I've-just-had-a-revelation.

"Of course. The marks on his neck, they weren't from bacteria infection. Anderson's an idiot! Well, we knew that already." Sherlock disappeared from his field of view. "Rope. Yes, there was something around his neck."

John felt cool material slide around his throat. _Oh God. This is a strangulation hazard, not hot bondage foreplay_, he told his raging libido. It ignored him in favour of playing with the thermostat of his body. The strap around his throat tighten. Not to the point that he was choking but just enough that he could feel his every breath and swallow. John's thoughts went hazy with desire.

Sherlock was muttering in excited tones behind him but John couldn't keep up with the words anymore. His knees were becoming sore and his left shoulder was protesting the awkward position but each throb of pain just sent more blood to his already straining erection.

Suddenly there was a tug on the restraint around his neck and he found his back flush against Sherlock's chest. The detective's mouth hovered just beside his ear and John could feel Sherlock's breath on his neck.

"You've been very good, John." Sherlock whispered. "You deserve a reward."

John groaned. Because no, Sherlock did not mean it like _that_. He was asexual and in a monogamous relationship with crime and—

Warm fingers brushed his side and skimmed lightly over his stomach.

"Anything." Came the husky whisper in his ear.

John's breath escaped on a moan.

"Do you have any idea how you look right now? Flushed, chest heaving with your breathes, your eyes half-lidded. You want this." Sherlock pulled John's head back till he was looking into piercing blue eyes. "Tell me know want this, John."

"I want this." John sobbed.

Sparks ignited in Sherlock's eyes. The hand on John's stomach swiped tantalizingly close to the place where he wanted it most.

"Tell me that I can do anything I want with you."

_YES! God, yes!_ "Anything" John breathed.

Sherlock's smile was positively sinful and John had one terrifying moment to think about what he had just agreed to before warm lips crashed down on his and he stopped thinking altogether.

Sherlock kissed much like he did everything else in life: unabashed, unapologetic, taking whatever the hell he wanted. Scorching. A clever tongue touched his lower lip demanding entrance, followed quickly by sharp teeth when he didn't part his lips fast enough. And then Sherlock's tongue was in his mouth, tracing the contours, learning it like a map. And John could taste him. Him and nothing else. And he tasted like danger.

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><p><strong>AN:** Part 2 will be up soon, just need to hammer out a few things.


	2. Chapter 2

**A/N:** I want to say thank-you to everyone that read this. My computer died last night so I've been a mass of frustration and unhappiness since. But the e-mails I kept getting from made me a bit happier. :)

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><p>John gave as good as he got. He had been wanting this (and yes, he could admit that now) for far too long, possibly from the very first moment that he had met Sherlock. Because of that impossibly sharp wit, that arrogant disregard for everyone's opinion of him and that manner he had of invading John's personal space, touching him like he had a right to do so. Which he didn't. But, God, was it ever hot!<p>

Sherlock's hand tangled in his hair and titled his head to a precise angle to maximize his access to John's mouth. Meanwhile his other hand stole down the front of John's trousers to cup him through the material.

John whimpered, thrusting into the pressure. His world was quickly narrowing to that hand and those long fingers and all the wicked things they could do.

And then suddenly he was yanked back by the cord around his neck and he should have toppled onto Sherlock. Only he had moved, _the bastard_, so he fell unceremoniously to the carpet instead.

"A little gentler maybe?" John grunted, the fall having knocked some sense back into him.

"Gentle. Is. Boring." Sherlock said, punctuating each word with a kiss to John's slightly abused neck and easily depriving him of sense once more.

"Well, I'm— ah, new to this." John mumbled and he wasn't sure whether he meant bondage, being with a man or just Sherlock in general.

The dark-haired man lifted his head to smirk at him. "Relax, you're doing fine."

John groaned as he recognized the phrase. "Please tell me you don't do this with the skull."

Sherlock's laugh was warm against his skin and John shivered. "No, only you."

John was pretty sure he shouldn't feel as flattered by that as he did. But it was rather difficult to care with Sherlock's lips wrapped around his collarbone.

Sherlock approached the problem of exploring John's chest systematically, like he had a planned out, logical guide to sex— which, of course, being Sherlock he probably did. He was also very thorough. _Too thorough_, John thought as Sherlock discovered first one erogenous zone, then another, and teased them mercilessly till John was a wreck. The words 'please' and 'Sherlock' appeared to be the only ones left in his vocabulary so he compensated by repeating them over and over again.

John's skin felt tight and his nipples ached from the attention that Sherlock was bestowing on them, laving and biting them by turns. Pleasure coursed through him like molten lava and he was sure that if this continued he would quite literally explode.

"pleasepleaseplease—SHERLOCK!"

One muscular thigh pushed its way between his and John sighed, rutting desperately against it. And then Sherlock's fingers were working at the belt of his trousers while he used his mouth to silence John's moans. His stomach tensed in expectation as the zipper was drawn down and then Sherlock's hand was on his cock. And it was glorious.

"What do you want, John?" Sherlock's voice was not entirely steady. "Do you want me to bring you off right now with my hand as you writhe on the floor?"

John whimpered. The hand gently stroked up and down his rigid flesh, pressure light. And not nearly enough.

"Do you want me to swallow you down?" Sherlock said against his mouth. _Yes, yes, God, yes._

Lithe fingers skimmed over the head of his cock.

"Or," Sherlock dragged his lips to John's ear. "Do you want me to just fuck you through the floor?" He growled.

John's moan was a drawn out 'yes' as he turned his head and captured Sherlock's mouth before he could make anymore lewd suggestions. The hand buried in John's pants tensed slight and John felt an answering hardness against his hip as Sherlock readjusted his weight. John took the only chance he was going to get to drive Sherlock even a fraction as crazy as John was, bucking his hips up against Sherlock's erection.

He felt more than heard Sherlock's groan and it sent a spark of pure satisfaction through him. The detective tore his mouth away from his and levelled him with a suspicious look.

"I see your heterosexuality is firmly out the window." He said with an arch of his brow.

"Shut up and fuck me!" And no, he didn't miss the way Sherlock's eyes widened slightly in shock as his pupils rapidly swallowed up the little colour there was in his eyes.

After that John's trousers and pants were removed in short order.

"You're wearing too many clothes." John observed with irritation. _If only he had his hands free, he would rip that shirt right off._

"And how much clothing do you want me to wear?" Was Sherlock's amused question as he stood up and began to unbutton his shirt.

Now there was a question John knew the answer to. "None."

Sherlock undressed with quick efficiency and not a hint of self-consciousness. Of course, that might have been because his body was perfect, all porcelain skin and sinewy muscle. John tried not to drool. _Really, how had he fooled himself into thinking that he was not incredibly attracted to this man?_

Now completely naked Sherlock knelt between John's legs and took hold of his cock. Slowly, keeping his gaze locked with John's, he lowered his mouth down till he could stick his tongue out and paint one broad line of heat from base to tip.

John threw his head back and cried out.

Sherlock, John found out quickly, wasn't teasing anymore. He licked, drew John's cock as far as he could into his mouth, ran his teeth lightly across the flesh. In short, he did everything to drive John completely out of his mind to the point where he didn't straight away notice the slick finger tracing his entrance.

Sherlock slowly worked his finger in and out. It felt strange but not unpleasant. And then Sherlock push his finger all the way in and hooked it and John saw stars. His back arched off the floor and he practically screamed.

"CHRIST!"

"I liked it more when you were saying my name." Sherlock commented, rubbing at the same spot with his finger before pulling out and adding another digit.

Ever the considerate friend, John instantly complied. "Sherlock, oh god, please!"

Soon John was reduced to incoherency as Sherlock steadily loosened the muscles of his entrance. When he pulled his fingers out John growled at the loss but soon he felt something much bigger nudging at his hole.

John swallowed convulsively.

"Relax" Sherlock said running his hands across John's stomach soothingly. And as John met Sherlock's eyes he saw the same anxiety reflected back at him.

He relaxed.

Sherlock pushed in slowly. It burned a little as unfamiliar muscles stretched inside him but he breathed through it. Finally, Sherlock was fully buried inside him and that thought alone was enough to make John roll his hips and grunt: "Move."

Sherlock drew out and thrust back in, in one smooth motion. And that— that was actually quite pleasant. And then Sherlock lifted his hips and hit that spot inside of him and it was suddenly much more than pleasant. It was exquisite.

They set up a fast rhythm, both wound too tightly to make this last. For every one of Sherlock's thrusts John would buck his hips up to meet him, his legs wrapped around Sherlock's waist. Before long their movements became erratic and the sounds falling from their lips lost all meaning.

John drew in air in short, sharp gasps, only enough to let him moan another syllable. His stomach clenched with every thrust. Sherlock's fingers dug into the flesh of John's buttocks so hard that John was pretty certain that he was going to have bruises there tomorrow and that was not as disturbing as it should be to a medical professional. But none of that mattered because he was close, so close. And then Sherlock grabbed the cord around his neck and yanked him right off the floor into a brutal kiss.

And that was all it took. John came apart shuddering, his world blanking out for one perfect moment before he collapsed in a boneless heap with Sherlock crushing him as he too reached his release.

They lay there for a few minutes getting their breath back before John decided that the pain in his shoulders outweighed the pleasure of having Sherlock's naked body draped across his.

"Do you mind untying me?" He asked hoarsely.

"Mm. I kind of like you tied up like this."

"Sherlock."

"Oh fine." He rolled off and undid the belt that held John's wrists together. Then ran his fingers around the strap at his neck but he didn't remove it. John didn't think it was healthy to exalt in such possessiveness but he couldn't help the flash of pleasure this caused.

"So," he asked casually. "The experiment was a success?"

Sherlock smiled. "It definitely warrants further research."

_Science is a wonderful thing_, John thought. His arms now free, he rolled his shoulders experimentally, wincing at the aches that caused. He really hoped Sherlock's next experiment involved a bed…

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><p><strong>AN:** Just so everyone knows, they used a condom. John was a bit too busy to notice but it was there… Practice safe sex kids.


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